Method for determining the moisture content in aggregates



Patented May 14, 192%..

pairs STATES PATENT OFFICE.

CHARLES S. JOHLESON, OF CHAMPAIGN, ILLINOIS.

No Drawing.

This invention relates generally to the art of making concrete, and more particularly to a method for determining the amount of moisture in aggregates having a variable moisture content.

.llt is well recognized that the strength of concrete depends largely upon the total water in the mix and that variations in the total water content cause unknown and undesir able variations in the strength of the concrete. F or this reason, to obtain concrete of uniform and predetermined strength, it is necessary to determine accurately the total amount oi water in each mix.

Commercial ljuiildiiig aggregates such as sand, gravel, etc, have a variable moisture content which not only ailects the apparent volumes of a quantity of aggregates of a given dry-aggregateoontent, but also affects the total water in the mix when the water and aggregates are proportioned independently of each other by volume or by weight, and then combined. Thus if a specified quantity water is combined with quantities of of variable moisture content which have been proportioned either by volume or by weight, the moisture in the aggregates is added to the water and thereby increases the total water in the mix to an unknown quantity. r

it is the general object of the invention to provide a method. whereby the moisture con tento't aggregates may be readily and accurately determined, thereby to permit an op erator to hold the total water in the mix constant by combining with the separately proportioned bulk aggregates a quantity of water such that the sum oi. the moisture con tent of the aggregates as determined by this method and that of the water added independently, equals a predetermined specified amount.

Another object is to provide such a process tor detcrmi .'.ng the moisture content oi commercial building; aggregates ct variable moisture content which lends itselt' readily to practical use and field application.

@ther objects and advantages will become apparent as the description proceeds.

It has been found as a result of a large number 01" experiments, that the specific gravity of building aggregates is remark ably constant even when these aggregates are Application filed. March 12, 1927. Serial in). 175,011.

obtained from widely separated sources. As the specific gravity of the aggregate, i. e., the specific gravity of the dry-aggregatecontent, remains unaffected by variations in moisture content, I utilize this characteristic as a basis for my invention.

The. invention contemplates a process whereby a sample of an aggregate is first weighed in air and is then weighed suspended in'water, provision being; inadcso that when the sample is weighed suspended in water the moisture already in the sample is permitted to combine with the water. The weight of the moisture in the original samplc is thereby automatically subtracted from the weight of the solid material so that the weight of the sample suspended in water in dicates the weight of the dry-aggrcgate-content of the oriqinal sau'iple. lainowing the specific gravitles of the aggregate and ot the water, the moisture content of the original sample may then be readily determined.

For the purpose of more fully describing the invention 1 shall, for an example, assume that commercial building aggregates have a specific g "avity of 2.7, that water weighs 62.5 pounds per cubic toot and has a specific gravity of 1.0, and that a sample of bulk aggregate is selected which weighs 17 pounds in air. If this sample contains only absolutely dry aggregate, i. e., aggregate having; no

moisture content, its weight suspended in.

water will equal the weight in air minus the loss in weight when sulm'iern'cd in water,

(Weight in air) or (weight in air) X625 or 17 or 17 6.3,

when submerged in water is 10 pounds, the

original sample contained 10.7- 10, or .7 pound of moisture. This is equal to .7 X 100 or 4.12%

moisture content, for the increased loss in Weight of the sample when Weighed submerged in water must have been due to the automatic subtraction of the Weight of the moisture in the sample which combined with v the Water.

equal to the weight in air of the sample, it is possible to determine the moisture content of thesample- The weighing of samples of the aggregates in air, and then weighing them submerged in water, constitutes a simple process by which the moisture content may be readily determined.

I claim as my invention:

1. As a step in the preparation of concrete, the process of determining the moisture content of aggregates of variable moisture content which includes weighing a quantity of an aggregate in air, placing said quantity in water so that the moisture in the combines with the water and then weighing the dry-aggregate-content of said quantity.

2. A process of determining the moisture content of aggregates which includes weighing a quantity of a normally moist aggregate in air, placing said aggregate in water so that the normal moisture thereof combines with the water and then weighing the dry-aggregate-content of said quantity submerged in water.

In testimony whereof, I hereunto aflixed my signature.

CHARLES S. JOHNSON aggregate 

